A recent demonstration by researchers in the Awschalom lab at the University of Chicago’s Institute for Molecular Engineering has shown that atomic scale defects in silicon carbide (SiC), a commercial semiconductor platform, can be tailored to create indistinguishable photons for scalable quantum communication technologies compatible with existing fiber optic networks. In order to distribute quantum entanglement over long distance, which is useful for creating secure lines of communication guaranteed by the laws of quantum mechanics, the photons emitted from different defects must be identical. The neutral divacancy defect in SiC has rapidly become a favorite candidate for creating a quantum information network since they were discovered by the Awschalom lab to possess excellent quantum mechanical properties for distributing quantum entanglement at telecom frequencies.

Until now, imperfections in the SiC crystal caused the photons emitted by different divacancies to have a wide range of frequencies. “What we discovered was that we could apply electric fields with conventional electronic gates to compensate for the different frequencies, and tune different divacancies to produce photons of the same frequency” said UChicago graduate student Charles de las Casas, the first author on the paper. In addition to providing a means of secure communication, the researchers believe this could one day link quantum computers together. “This was a crucial step toward entangling divacancies over long distances,” said David Awschalom, the Liew Family Professor in Spintronics and Quantum Information at the Institute for Molecular Engineering and lead author on the paper. “These results give us hope that silicon carbide could one day form the backbone of a quantum internet,” Awschalom added. The publication was recently selected as an Editor’s Choice in Applied Physics Letters.

Indistinguishable photons that are linked in frequency can be created from separate pieces of silicon carbide, a commercial semiconductor platform, when voltages are carefully applied.